In the README, you can find further details about how to download the
image from docker hub and how to start using it.

We encourage developers to use this image for development & testing if
they plan to deploy their Swift applications to a Cloud Foundry
environment. This docker image uses Ubuntu 14.04 which is the same Linux
flavor used by Cloud Foundry-based offerings. We have seen several cases
where developers use docker images based on Ubuntu 16.04 or 15.10 and then
run into unexpected problems when running their apps on cloud offerings
based on Cloud Foundry. Also, this docker image has been hardened to meet
basic guidelines and common practices from a security perspective (for
further details, see the Vulnerability Advisor documentation for docker
images: https://www.ibm.com/blogs/bluemix/2015/07/vulnerability-advisor/).